Multifunctional Solid-State Carbon Dots Enabling Multicolor Stretchable AC Electroluminescent Devices for Intelligent Human Motion Monitoring

Multicolor stretchable alternating‑current electroluminescent (ACEL) devices hold promise for next‑generation flexible and wearable electronics, yet conventional color‑conversion materials are often limited by high cost, poor operational stability, and complex architectures. Here, solid‑state carbon dots (CDs) with emission spanning the yellow-to-red spectral region were synthesized from terephthalaldehyde and p‑Phenyldiacetonitrile. These CDs exhibit exceptional fluorescence stability under AC fields, retaining over 85% color‑conversion efficiency after 96 h of operation, together with excellent resistance to photodegradation after 96 h of UV exposure, demonstrating their suitability for AC‑driven electroluminescent systems. A single electrospun functional layer incorporating CDs as color-conversion centers was constructed to realize a simplified multicolor ACEL architecture. By tuning the CDs concentration and driving frequency, emission color could be continuously modulated from blue to white (CIE: 0.30, 0.33), orange, and green. Studies revealed that the dielectric properties of CDs crucially regulate the internal electric field distribution. Notably, adding yellow‑emissive CDs increased luminance by 26.60% while enabling efficient color conversion. Furthermore, integration with a resistive sensor and Bluetooth chips allowed real‑time visual monitoring of human joint movements. This work establishes a versatile strategy for developing multifunctional stretchable ACEL systems and highlights their significant potential for smart wearable electronics, health monitoring, and human–machine interaction.